Method for reducing pollution in foundries

ABSTRACT

This invention relates to a method for reducing dust pollution in foundries that use sand molds for casting and recycle the used sand for subsequent molding operations. A quantity of sand is added to the used sand, preferably at the shakeout, so that the total amount of said weighs at least 12 times the weight of the metal previously cast.

United States Patent Schumacher 5] *Mar. 7, 1972 [54] METHOD FOR REDUCING POLLUTION [58] Field oi Search ..164/5 IN FOUNDRIES Ci 56 References ted [72] Inventor: Joseph S. Schumacher, Cincinnati, Ohio I l [73] Assignee: International Minerals and Chemical Cor- UNITED STATES PATENTS poration, Skokie, 3,461,941 8/1969 Schumacher ..164/5 Notice: The portion of the term of this patent subsequent to Aug. 19, 1986, has been dispmfmry f P overholser c|aimed Assistant Exammer-John E. Roethel AttorneyWood, Herron & Evans [22] Filed: Oct. 15, 1969 [21] Appl. No.: 866,716 AB TRACT This invention relates to a method for reducing dust pollution Application Data in foundries that use sand molds for casting and recycle the i n-p of .3611 Apr. used sand for subsequent molding operations. A quantity of 1969, Whlch IS a continuation-impart 0f Sell sand is added to the used sand, preferably at the shakeout, so 3 19, 1968 3,461,941- that the total amount of said weighs at least [2 times the weight of the metal previously cast. [52] 0.8. Cl. ..164/5 [51 Int. Cl ..B22d 29/00 9 Claims, No Drawings METHOD FOR REDUCING POLLUTION IN FOUNDRIES CROSS REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of my prior application, Ser. No. 839,339 filed Apr. 7, 1969 which in turn is a continuation-in-part of Ser. No. 714,339, filed Mar. 19, 1968, now U.S. Pat. No. 3,46l.94l.

BACKGROUND OF THE INVENTION In recent years there has been increased activity in many segments of industry to devise better equipment and methods for reducing air pollution. This has been especially true in the foundry industry. Also in recent years governmental agencies, state, local, and federal, have adopted and enforced more stringent pollution laws and ordinances. Such legislation has included the foundry industry.

One of the principal sources of pollution in a foundry is from sand which has been used in the molding operation. After the molding, the sand molds and the castings. are separated and the sand is reclaimed for reuse. During at least a part of this reclaimation process the sand is hot. Consequently, a great deal of dust is expelled into the atmosphere. A large part of this dust occurs at the shakeout since this is the point at which the sand is at its hottest temperature before the next molding operation. As the sand is conveyed from the shakeout additional pollution occurs.

In order to combat this type of pollution, foundries have utilized various types of devices. An idea of how sizeable the market for such devices is can be gleaned from an examination of the foundry periodicals. Such periodicals also present a reliable indicator for how serious the problem is, some even dedicating entire sections of each issue to the problems and supposed solutions.

Many of the various types of pollution equipment proposed for foundry use are expensive and require constant maintenance. By reason of the initial costs and the subsequent maintenance costs, many smaller foundries are not able to afford the required equipment. Unfortunately too, is the fact that some of the equipment is unable to satisfactorily perform its function.

SUMMARY OF THE INVENTION -In my prior application and patent, I have disclosed methods for cooling foundry sand after molding and before reuse. The processes are based on the principle of adding a quantity of relatively cool sand to a quantity of relatively hotter sand for the purpose of reducing the temperature of the hot sand. Disclosed also is the fact that such a process can reduce pollution and eliminate costly pollution equipment. I have found that If a quantity of sand is added at or near the shakeout to the hot used sand such that the total mass is at least equal to 12 times the weight of the metal cast, that this source of air pollution is substantially eliminated. Since this source constitutes about 50% of the total pollution involved it is indeed a substantial amount.

PREFERRED EMBODIMENTS AND DESCRIPTION In the casting of metals into sand molds, the amount of sand used to form a mold is usually expressed as a function of the amount of metal to be poured into it. This relationship is called the sand to metal ratio. For example, sufficient sand can be used for the mold to give a sand to metal ratio of from 3 to l to to 1. While these ratios are frequently used, others are often times used too. A common ratio used is a ratio of about 6 to 1. That is, a mold is formed which consists of 6 pounds of sand for each pound of metal to be cast.

Foundry sand is, of course, not sand alone but contains additional constituents such as clays and/or carbons and/or other additives and/or temper water. Carbons in common use are powdered coal, coal tar, pitch, asphalt, graphite and coke. Other additives can be added such as celluloses, cereal binders, etc. After one or more molding operations new sand and/or clays and/or carbons can be added to the used sand to replace the portion of the original sand which has been made unuseable. Temper water is also frequently added in minor amounts. The following is a typicaltable which shows the amount of additives which usually must be added after the batch of sand has-been used. This table is for ferrous metals other than steel. Other data for nonferrous metals, steel and ductile metals is known to those in the foundry industry.

lutants expelled from hot foundry sand can be very substantially reduced if enough relatively cool sand is added to the hot sand so that a sand to metal ratio of l2/l or greater is obtained. Preferably the relatively cool sand is added at or near the shakeout since this is the point at which this type of air pollution begins. Of course, the relatively cool sand could be added later but then all of the benefits of this process would not be obtained. It also may be desirable to add at the shakeout whatever additives are to be added to reconstitute the new sand. Additions at such point also serve to reduce air pollution.

A typical foundry installation isshown at pages 8 and 9 of the Oct., 1967 Foundry Age Magazine. To operate this system using my process one would proceed as follows. Assuming that the system was to be operated at a sand to metal ratio of 4 to i then at the shakeout a quantity of relatively cool sand, having a temperature of preferably ambient temperature, would be added as to produce a sand to metal ratio of [2/ i. As desired, the 12/ l mixture of sand produced can be all returned to the muller and mulled or only a portion thereof may be mulled, the remaining portion being diverted to a storage tank for subsequent pollution reduction.

At a sand to metal ratio of l2/l or above, the mixture of hot and cool sand at the shakeout is relatively cool and relatively moist. Thus a major source of pollution is contained. While sand to metal ratios of less than 12] i may be produced at the shakeout, the lower the ratio the more pollution will occur. Consequently, I prefer to use a 12/ 1 ratio or more.

It can be seen that my process provides a simple, yet efficient method for reducing air pollution. All that is required in addition to the conventional equipment needed is the additional amount of sand and perhaps a slight additional amount I breaking said molds and separating the metal from said used sand, and

cooling said used sand by mixing with it at the shakeout or immediately adjacent thereto said major portion of sand whereby the mixture has a temperature of below 120F. 2. The foundry process of claim 1 wherein the molds have a weight of about four times the weight ofthe material to be cast and the weight of the major portion is at least 16 times the weight of the metal to be cast.

3. The process of claim 1 wherein minor amounts of additives are added to the used sand.

4. The process of claim 1 wherein the temperature of said major portion is less than 90 F.

5. A foundry process for cooling foundry sand and for reducing foundry pollution which comprises mulling used sand to provide a quantity of sand of at least as great as 12 times the weight of the metal to be cast, said used sand derived from a later step in the process,

forming molds from a minor portion of the mulled mixture, said molds each having a weight of at least three times the weight of the material to be cast,

retaining the major portion of foundry sand for the later cooling of said minor portion,

casting metal in the molds,

separating the metal from said molds,

cooling said used sand by mixing with it at the shakeout or immediately adjacent thereto said major portion of sand whereby the mixture has a temperature of below 120F., and

returning the minor and major portions of sand to the aforesaid mulling step.

6. The foundry process of claim 5 wherein the molds have a weight of about four times the weight of the material to be cast and the weight of the major portion is at least 16 times the weight of the metal cast.

7. The foundry process of claim 6 wherein minor amounts of additives are added to the mixture of the major and minor portions of sand.

8. The foundry process of claim 6 wherein the temperature of said major portion is less than 90 F.

9. In a process for making greyiron castings wherein sand molds are formed on the basis of a sand to metal ratio of at least 3 to 1 wherein a larger quantity is used to cool the sand after molding and shakeout, the improvement which is adapted to reduce pollution comprising adding at least one additive member of the group consisting of sand, clays, and carbons to the used sand at the shakeout, or immediately adjacent thereto, the amounts ofsaid additive member added being calculated from the following formula:

number of pounds of new sand (.4/2000 X8 wherein A the number of pounds of used sand and B where the sand to metal ratio is 3/ 1 75 where the sand to metal ratio is 4/1 60 where the sand to metal ratio is 5/ 1 50 where the sand to metal ratio is 6/ 1 37.5 where the sand to metal ratio is 8/ 1 30.0 where the sand to metal ratio is 10/ 1 25.0 where the sand to metal ratio is 12/ 1 21.4 where the sand to metal ratio is 14/ 1 18.7 where the sand to metal ratio is 16/ 1 16.6 where the sand to metal ratio is 18/1 15.0 where the sand to metal ratio is 210/1 number of pounds of bentonite clays .4/2000 XC wherein A the number of pounds of used sand and C= 18.8 where the sand to metal ratio is 3/1 14.4 where the sand to metal ratio is 4/ 1 1 1.3 where the sand to metal ratio is 5/ l 9.41 where the sand to metal ratio is 6/ 1 7.15 where the sand to metal ratio is 8/ 1 5.65 where the sand to metal ratio is 10/ 1 4.71 where the sand to metal ratio is 12/ 1 4.05 where the sand to metal ratio is 14/ 1 3.60 where the sand to metal ratio is 16/ 1 3.15 where the sand to metal ratio is 18/1 2.83 where the sand to metal ratio is 20/ 1 and the number of pounds of carbons A/2000 X D wherein A =the number of pounds of used sand and D 16 where the sand to metal ratio is 3/ 1 1 1.9 where the sand to metal ratio is 4/1 9.5 where the sand to metal ratio is 5/1 8.0 where the sand to metal ratio is 6/ 1 6.03 where the sand to metal ratio is 8/1 4.75 where the sand to metal ratio is 10/1 4.0 where the sand to metal ratio is 12/1 3.43 where the sand to metal ratio is 14/ 1 3.03 where the sand to metal ratio is 16/1 2.66 where the sand to metal ratio is 18/1 2.40 where the sand to metal ratio is 20/ 1 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,646 987 r Dated Mgrch 7, 1972 v Inventor (s) Joseph S. Sehumacher It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the abstract, line 5, "said" should be -'-send--.

Column 1, line 5, "'Apr. 7, 1969" should be --July 7, l969- Column 2, line 19, second column, "18/8 lb." should be -l8.8 lb.--

Column 2, line 34, after "sand", ":i.s" sh'ould he -should be".

Column 3, line 44, after ;'l" and before "wherein" insert "and" Column 4, line '6, delete between and "A".

Signed and sealed this 11131 day of July 1972.

(SEAL) Attest:

EDWARD M'.FLE'ICHER, JR. ROBERT GOTTSCHALK Attes ting Officer Commissioner of Patents FORM F'O-IOSO (10-69) usco c eoanmes i ".5. GOVIINIENT HUNTING OFFICE: "l9 O-q." A 

2. The foundry process of claim 1 wherein the molds have a weight of about four times the weight of the material to be cast and the weight of the major portion is at least 16 times the weight of the metal to be cast.
 3. The process of claim 1 wherein minor amounts of additives are added to the used sand.
 4. The process of claim 1 wherein the temperature of said major portion is less than 90* F.
 5. A foundry process for cooling foundry sand and for reducing foundry pollution which comprises mulling used sand to provide a quantity of sand of at least as great as 12 times the weight of the metal to be cast, said used sand derived from a later step in the process, forming molds from a minor portion of the mulled mixture, said molds each having a weight of at least three times the weight of the material to be cast, retaining the major portion of foundry sand for the later cooling of said minor portion, casting metal in the molds, separating the metal from said molds, cooling said used sand by mixing with it at the shakeout or immediately adjacent thereto said major portion of sand whereby the mixture has a temperature of below 120* F., and returning the minor and major portions of sand to the aforesaid mulling step.
 6. The foundry process of claim 5 wherein the molds have a weight of about four times the weight of the material to be cast and the weight of the major portion is at least 16 times the weight of the metal cast.
 7. The foundry process of claim 6 wherein minor amounts of additives are added to the mixture of the major and minor portions of sand.
 8. The foundry process of claim 6 wherein the temperature of said major portion is less than 90* F.
 9. In a process for making greyiron castings wherein sand molds are formed on the basis of a sand to metal ratio of at least 3 to 1 wherein a larger quantity is used to cool the sand after molding and shakeout, the improvement which is adapted to reduce pollution comprising adding at least one additive member of the group consisting of sand, clays, and carbons to the used sand at the shakeout, or immediately adjacent thereto, the amounts of said additive member added being calculated from the following formula: number of pounds of new sand (A/2000 X B wherein A the number of pounds of used sand and B 100 where the sand to metal ratio is 3/1 75 where the sand to metal ratio is 4/1 60 where the sand to metal ratio is 5/1 50 where the sand to metal ratiO is 6/1 37.5 where the sand to metal ratio is 8/1 30.0 where the sand to metal ratio is 10/1 25.0 where the sand to metal ratio is 12/1 21.4 where the sand to metal ratio is 14/1 18.7 where the sand to metal ratio is 16/1 16.6 where the sand to metal ratio is 18/1 15.0 where the sand to metal ratio is 20/1 number of pounds of bentonite clays A/2000 X C wherein A the number of pounds of used sand and C 18.8 where the sand to metal ratio is 3/1 14.4 where the sand to metal ratio is 4/1 11.3 where the sand to metal ratio is 5/1 9.41 where the sand to metal ratio is 6/1 7.15 where the sand to metal ratio is 8/1 5.65 where the sand to metal ratio is 10/1 4.71 where the sand to metal ratio is 12/1 4.05 where the sand to metal ratio is 14/1 3.60 where the sand to metal ratio is 16/1 3.15 where the sand to metal ratio is 18/1 2.83 where the sand to metal ratio is 20/1 and the number of pounds of carbons A/2000 X D wherein A the number of pounds of used sand and D 16 where the sand to metal ratio is 3/1 11.9 where the sand to metal ratio is 4/1 9.5 where the sand to metal ratio is 5/1 8.0 where the sand to metal ratio is 6/1 6.03 where the sand to metal ratio is 8/1 4.75 where the sand to metal ratio is 10/1 4.0 where the sand to metal ratio is 12/1 3.43 where the sand to metal ratio is 14/1 3.03 where the sand to metal ratio is 16/1 2.66 where the sand to metal ratio is 18/1 2.40 where the sand to metal ratio is 20/1 